The effects of nerve stimulation, in the presence and absence of drugs which enhance neurally mediated release of catecholamines, on tyrosine hydroxylase activity in intact tissue and on the kinetic properties of the partially purified enzyme will be systematically investigated in isolated cat spleen, guinea-pig vas deferens-hypogastric nerve preparation, and rat brain striatum. The effects of heparin, phosphatidyl-L-serine, cyclic AMP-dependent protein kinase and a calcium binding activator of adenylate cyclase on tryosine hydroxylase isolated from control and stimulated tissues will be examined. Molecular changes in the enzyme during activation and the time course of neurally induced activation of the enzyme will be studied, with particular emphasis on possible enzyme phosphorylation. Regulation of catecholamine release by nerve stimulation will be evaluated and correlations will be made with regard to the effects of cholinergic and adrenergic agonists, alpha and beta adrenergic blocking agents, prostaglandins and cyclic nucleotide analogs on neurotransmitter release and tyrosine hydroxylase activation. The role of cyclic nucleotides in the induction of tyrosine hydroxylase will also be assessed both in mouse neuroblastoma cells in culture and in cat adrenal glands in vivo and in induction will be correlated with acute changes in cyclic nucleotide levels and cyclic AMP-dependent protein kinase activity in these tissues. The ultrastructural localization of tyrosine hydroxylase will be determined by immunocyto-chemical techniques and changes in the ultrastructural distribution of the enzyme with nerve stimulation will be assessed. Amino acid aminotransferases, keto acids, other endogenous substances and drugs will be evaluated with regard to their effects on maintenance of releasable neurotransmitter stores during prolonged nerve stimulation.